Method for reporting channel state information and device thereof

0001A method and device for reporting channel state information This application requires a Chinese patent application filed on May 07, 2010 with the application number 201010171368.6 and the invention titled "a method and device for reporting channel state information". Priority, the entire contents of which are incorporated in this application by reference. Technical field

0002The present invention relates to the field of wireless communication, and in particular, to a method and device for reporting channel state information. Background technique

0003In a point-to-point communication system, if the transmitter can obtain certain channel state information (Channel State Information, CSI), it can optimize the spatial distribution characteristics of the modulation mode, coding rate and signal power of the transmitted signal, so that the transmitted signal and the channel can propagate The characteristics are matched, so that the effect of enhancing the reliability of signal reception and reducing the complexity of the reception algorithm can be achieved. In a multi-user system, the transmitter can make scheduling decisions based on the CSI obtained by it, so as to achieve improvement in system spectrum efficiency and avoid interference between cells.

0004In LTE (Long-Term Evolution, Long-Term Evolution) Rd-8/9, eNB (evolved base station) can use channel reciprocity or UE (User Equipment, user equipment) feedback to obtain the CSI of the downlink channel, where PDSCH (Physical Downlink Shared Channel (Physical Downlink Shared Channel) uses several codebook-based implicit CSI feedback methods for several main transmission modes. In transmission modes 4, 5, 6 (and PMI (Precooding matrix indication, precoding matrix indication) reporting mode in transmission mode 8), the UE measures the downlink channel based on the CRS (Cell-specific Reference Signal, common reference symbol), and according to its The own receiving and processing algorithm reports to the eNB the number of data streams (RI, Rank Indication, rank indicator) and the number of the precoding matrix (PMI, that is, the precoding matrix indicator) that the downlink can support, and the UE also needs to report each Channel quality indication (Channel Quality Indication, CQI ). During the calculation of the CQI, the UE assumes that the eNB uses its recommended RI/PMI.

0005The codebook-based precoding scheme adopted in LTE Rd-8/9 mainly focuses on single-user application scenarios, while Rel-10 (LTE-A, That is, LTE-Advanced) will further optimize the precoding and its feedback mechanism to better support multi-user scenarios. According to the current discussion results, the basic requirements of the LTE-A for the feedback enhancement scheme are: On the premise of keeping the feedback overhead low, the CSI feedback accuracy is improved as much as possible. Under the above background, it has basically been determined that a feedback scheme based on dual codebooks will be adopted in Rd-10. In this scheme, the channel information is divided into relatively stable long-term/broadband CSI and short-term/frequency-selective CSI with higher time/frequency selectivity. The UE can separately quantize the above CSI with two codebooks according to different feedback cycles, and feed back the corresponding PMI. PMI-1, which reflects long-term/broadband CSI, has a higher spatial resolution, but can be fed back in a larger cycle and in a larger bandwidth unit. PMI-2 is used to reflect the rapidly changing part of CSI, and needs to be fed back in a subband unit with a lower feedback period. Since the equivalent channel matrix formed by the combination of the channel and PMI-1 may have a lower dimensionality, generally speaking, PMI-2 only needs to quantize the CSI of a lower dimensionality, so PMI-2 has fewer bits.

0006In the current version of LTE (Rel-8/9), higher layers can configure the UE to use PUCCH (Physical Downlink Control Channel) for periodic reporting and/or use PUSCH (Physical Uplink Shared Channel, physical uplink sharing) Channel) for acyclic reporting. According to the existing specifications and the Way forward reached in the current LTE-A discussion, the reporting content and reporting process of PUCCH and PUSCH should be completely independent. Table 1 and Table 2 give the reporting modes based on PUCCH and PUSCH in the existing specifications, respectively. Among them, PUCCH report mode (report mode) is a combination of PUCCH report type (report type), and the corresponding relationship is shown in Table 3.

0007Table 1: PUCCH-based reporting mode

0008PMI Feedback Type <img file="WO2011137726A1_D0001.tif" />

0009Table 2: PUSCH-based reporting mode

0010<img file="WO2011137726A1_D0002.tif" />

0011Table 3: Report types and number of bits included in each PUCCH reporting mode <img file="WO2011137726A1_D0003.tif" />

0012In the process of implementing the present invention, the inventor found that the existing technology has the following defects: On the one hand, the existing feedback mechanism cannot achieve two-level feedback; on the other hand, the reporting content and reporting of PUCCH and PUSCH in the existing feedback mechanism The process should be completely independent, and in fact the information provided by the two reporting channels may be somewhat redundant. If dual codebook feedback is supported in both PUCCH and PUSCH, it is inevitable to add a new reporting mode (reporting mode). In addition, if it is required to independently support two-level feedback in PUCCH and PUSCH reporting, it may cause an increase in feedback overhead. Summary of the invention

0013Embodiments of the present invention provide a method and apparatus for reporting channel state information, which are used to implement reporting of information state information through PUCCH and PUSCH based on a two-level codebook.

0014The method for reporting channel state information provided by an embodiment of the present invention includes:

0015The user terminal selects the codebook used for reporting the precoding matrix indicator PMI from the two-level codebook, and selects the PMI from the codebook; the two-level codebook includes a codebook reflecting long-term/broadband information and reflecting short-term/frequency Codebook for selective channel information;

0016The user terminal determines a parameter used when calculating the channel quality indicator CQI, and calculates the CQI according to the parameter; wherein, when reporting through the PUCCH, the determined parameter used in calculating the CQI includes the PMI reported by the user terminal through the PUSCH When reporting through the PUSCH, the determined parameters used in calculating the CQI include the PMI reported by the user terminal through the PUCCH; the user terminal reports the RI, the selected PMI and the calculated according to the specified reporting mode

0017CQI.

0018The terminal device provided by the embodiment of the present invention includes:

0019The PMI selection unit is used to select the codebook used for reporting the precoding matrix indicator PMI from the two-level codebook and select the PMI from the codebook; the two-level codebook includes a codebook reflecting long-term/broadband information and Codebook reflecting short-term/frequency selective channel information;

0020A CQI calculation unit, used to determine the parameters used when calculating the channel quality indicator CQI, and calculate the CQI according to the parameters; wherein, when reporting through the PUCCH, the determined parameters used in calculating the CQI include the user terminal reporting through the PUSCH PMI; when reporting through PUSCH, the determined parameters used in calculating CQI include the PMI reported by the user terminal through PUCCH;

0021The reporting unit is configured to report the RI, the PMI selected by the PMI selection unit, and the CQI calculated by the CQI calculation unit according to the specified reporting mode.

0022In the above embodiment of the present invention, on the one hand, by setting a two-level codebook, the two-level codebook includes a codebook reflecting long-term/broadband information and a codebook reflecting short-term/frequency selective channel information. The reporting method selects the corresponding codebook and then the corresponding PMI, so as to meet the requirements of PUCCH and PUSCH reporting channel status information; on the other hand, when calculating the CQI, the PUCCH and PUSCH reporting mechanism is combined, so that the existing PUCCH can be used With the PUSCH reporting mechanism, the channel state information can be uploaded without additional overhead. BRIEF DESCRIPTION

0023FIG. 1 is a schematic flowchart of reporting channel state information based on PUCCH in an embodiment of the present invention; FIG. 2 is a schematic flowchart of reporting channel state information based on PUSCH in an embodiment of the present invention; FIG. 3 is a schematic structural diagram of a terminal device according to an embodiment of the present invention . DETAILED DESCRIPTION Embodiments of the present invention provide a channel state information reporting scheme, which is suitable for a precoding process that uses a two-level codebook. In this solution, the UE may report RI, long-term/broadband PMI and corresponding CQI information to the eNB through the PUCCH, and may report the short-term/frequency selective PMI and corresponding CQI information of multiple subbands to the eNB in combination with the PUSCH.

0024The technical solutions in the present invention will be clearly and completely described below in conjunction with the drawings and specific embodiments in the present invention. Obviously, the described embodiments are part of the embodiments of the present invention rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by a person of ordinary skill in the art without creative efforts fall within the protection scope of the present invention. The two-level codebook in the embodiment of the present invention is a codebook reflecting long-term/broadband information and a codebook reflecting short-term/frequency selective channel information, respectively. The codebook is a set of preset precoding matrices. For ease of description, in the embodiment of the present invention, the codebook reflecting long-term/broadband information is denoted as CB1, and the codebook reflecting short-term/frequency-selective channel information is denoted as CB2. Since the feedback enhancement is mainly used in the MU-MIMO (MultiUsers-Multiple Input Multiple Output, multi-user-multiple input multiple output) scenario (low rank), the two-level codebook structure can be expressed as:

0025RI&lt;R_T, The dimension of PMI-1 is Ν Ι^, and the dimension of PMI-2 is χ RI (where is the number of eNB transmit antennas, R_TIs the set threshold, which can be determined according to the rank number of MU-MIMO);

0026RI> R_T, PMI-1 is fixed at N_T X Ν_τ (Denoted as), and the dimension of PMI-2 is Ν_τ χ RI (where ^ is the number of base station transmit antennas, R_TIt is a set threshold, which can be determined according to the rank number of MU-MIMO).

0027In the embodiment of the present invention, the reporting of channel information is divided into two parts: PUCCH reporting and PUSCH reporting. There is a certain dependency relationship between the two parts of information, specifically:

0028In the process of reporting channel state information based on PUCCH, the UE may report RI and PMI through PUCCH reporting model-1, 2-1 according to the period and timing offset configured by the higher layer_PUCCHAnd the corresponding channel quality indicator CQI_PUCCH. Where PMI_PUCCHDefinition and CQI_PUCCHCan be expressed as:

0029RIR_TAt this time, the UE selects a precoding matrix PMI suitable for the full bandwidth from CB1 according to the downlink channel conditions and the detection algorithm_PUCCH=PMI-l e CBl, in implementation, the PMI_PUCCHFor the best precoding matrix, the best precoding matrix in this application refers to the precoding matrix that can maximize the downlink transmission rate. The UE side may calculate the transmission rate that can be obtained when using each precoding matrix in the codebook one by one, and then determine the best precoding matrix according to the available rate. The UE calculates CQIPUCCH=CQI(RI,PMI-1,PMI-2) and reports it assuming that the eNB uses its reported RI, PMI-1 and PMI-2 (PMI-2 is reported by PUSCH);

0030RI>R_TAt this time, the UE selects a precoding matrix PMI suitable for the full bandwidth from CB2 according to the downlink channel conditions and the detection algorithm_PUCCH=PMI-2e CB2, under implementation, the PMI_PUCCHIt is the best precoding matrix. UE calculates CQIPUCCH=CQI(RI, I under the assumption that eNB uses its recommended RI and PMI-2_NR , PMII-2) and report. In the process of reporting channel state information based on PUSCH, the UE can report RI and PMI through PUSCH reporting mode3-1, 1-2, 2-2 according to the period and timing offset configured by the higher layer_PUSCH And the corresponding channel quality indicator CQI_PUSCH. Where PMI_PUSCHDefinition and CQI_PUCCHCan be expressed as:

0031RIR_TAt this time, the UE selects the precoding matrix PMI for each frequency domain reporting unit from CB2 according to the downlink channel condition detection algorithm and the PUSCH reporting mode configured by the higher layer (depending on the reporting mode, the reporting unit may be broadband or subband)_PUSCH=PMI-2e CB2, under implementation, the PMI_PUSCHIt is the best precoding matrix. The UE calculates CQIPUSCH=CQI(RI, PMI-1, PMI-1) and reports it assuming that the eNB uses its reported RI, PMI-1 (PMI-1 is reported by PUCCH) and PMI-2;

0032RI>R_TAt this time, the UE selects the precoding matrix PMI for each frequency domain reporting unit (based on the reporting mode, the reporting unit may be broadband or subband) according to the downlink channel conditions, detection algorithm, and PUSCH reporting mode configured by the higher layer_PUSCH=PMI-2e CB2, under implementation, the PMI_PUSCH It is the best precoding matrix. UE calculates CQI under the assumption that eNB uses its recommended RI and PMI-2_PUCCH=CQI(RI, I_NR , PMII-2) and report.

0033In the process of reporting information based on PUCCH and the process of reporting based on PUSCH, the function CQI(x, y, z) indicates that the UE assumes that the rank of the channel is x, and the eNB uses PMI-l=y and PMI-2=z. The corresponding synthetic precoding matrix PM=G(PMI-1, PMI-2). The function G() represents the function of synthesizing the precoding matrix from the two-level PMI. Among them, the function G() can be implemented by an existing algorithm or other algorithms, for example, G (X, y) = x*y.

0034In the following, with reference to FIGS. 1 and 2, a high-level configuration UE is used as an example to use PUCCH reporting mode 1-1 and PUSCH reporting mode 1-2, respectively for the process of reporting channel state information based on PUCCH and the reporting of channel state information based on PUSCH The process is described.

0035As shown in FIG. 1, the process of reporting channel state information based on PUCCH can be expressed as follows: Step 401: The UE calculates the RI.

0036In this step, the UE may measure the downlink channel based on the CRS, and use the measured downlink channel performance parameter to calculate the number of data streams (RI) that the UE can support in the downlink according to its own reception processing algorithm. Step 402: The UE judges whether the calculated RI exceeds R_TIf it does not exceed, go to step 403; if it exceeds, go to step 404.

0037Step 403: When the UE determines that RIR_TAt this time, the UE selects the best precoding matrix PMI suitable for the full bandwidth from CB1 according to the downlink channel conditions and the detection algorithm_PUCCH=PMI-l e CBl. In addition, the UE assumes that the eNB uses the RL PMI-1 and PMI-2 reported by it (PMI-2 is reported by the PUSCH), and calculates the full bandwidth CQI based on the above assumption_PUCCH=CQI(RI,PMI-1,PMI-2), and then go to step 405.

0038Step 404, RI>R_TAt this time, the UE selects the best precoding matrix PMI-2 suitable for the full bandwidth from CB2 according to the downlink channel conditions and detection algorithm, and calculates the CQI of the full bandwidth_PUCCH=CQI(RI, I_Nr , PMII-2), and then go to step 405.

0039Step 405: The UE reports the channel state information through the PUCCH and using the reporting mode 1-1 configured for it according to the period and timing offset configured by the higher layer. The channel state information may include: the RI calculated by the UE, the selected PMI_PUCCH, And the calculated CQI_PUCCH。

0040As shown in FIG. 2, the process of reporting channel state information based on PUSCH can be expressed as: Step 501: The UE calculates the RI.

0041In this step, the UE may measure the downlink channel based on the CRS, and use the measured downlink channel performance parameter to calculate the number of data streams (RI) that the UE can support in the downlink according to its own reception processing algorithm.

0042Step 502: The UE judges whether the calculated RI exceeds R_TIf not exceeded, go to step 503; if exceeded, go to step 504.

0043Step 503: When the UE determines that RIR_TAt this time, the UE selects the best precoding matrix PMI for each subband from CB2 according to the downlink channel conditions and the detection algorithm_PUSCH=PMI-2e CB2. Moreover, the UE assumes that the eNB uses its reported RI and PMI-1 (PMI-1 is reported by PUCCH) at full bandwidth and that the eNB uses its reported subband PMI-2 on each subband, based on the above Assuming calculation of CQI for full bandwidth_PUSCH=CQI(RI,PMI-1,PMI-2), and then go to step 505.

0044Step 504, RI>R_T, The UE selects the best precoding matrix PMI for each subband according to the downlink channel conditions and detection algorithm_PUSCH=PMI-2e CB2. And the UE assumes that the eNB uses its recommended RI and PMI-2 of each subband in the full bandwidth, and calculates CQIPUSCH=CQI(RI, I on the full bandwidth based on the above assumptions_NR , PMI-2), and then go to step 505.

0045Step 505: The UE reports the channel state information through the PUSCH and using the reporting mode 1-2 configured for it according to the period and timing offset configured by the higher layer. The channel state information may include: the RI calculated by the UE, the selected PMI_PUSCH, And the calculated CQI_PUSCH。

0046In another embodiment of the present invention, R may not be preset_T (Or by setting a large enough R_TSo that RI can always satisfy RI&lt;R_T ), so that the user terminal does not need to RI and R_TFor comparison, instead of directly selecting PMI from CB 1 when reporting channel state information through PUCCH, and using PMI reported through PUSCH as one of the parameters when calculating CQI; similarly, when reporting channel state information through PUSCH , Directly select PMI from CB2, and use the PMI reported through PUCCH as one of the parameters when calculating CQI. The processing procedures of the corresponding steps are similar to the corresponding steps of FIG. 1 and FIG. 2 and will not be repeated here.

0047In the implementation, setting Rt to be adjustable can increase the flexibility. In specific practice, if you want a simpler system design, you can remove this function.

0048It can be seen from the above description that, in the foregoing embodiments of the present invention, the existing feedback channels (PUCCH and PUSCH) are used to implement two-level feedback. Among them, the reporting contents of PUCCH and PUSCH complement each other, thereby reducing information redundancy. In addition, in this embodiment of the present invention, it is not necessary to introduce an additional reporting type and a reporting mode, so the impact on the existing channel state information reporting mechanism is small, and no additional signaling overhead is required.

0049Based on the same technical concept, embodiments of the present invention also provide a terminal device.

0050As shown in FIG. 3, the terminal device provided by the embodiment of the present invention may be applied to the process of reporting channel state information through PUCCH and PUSCH. The terminal device may include: a PMI selection unit 601, a CQI calculation unit 602, and a reporting unit 603, where :

0051PMI selection unit 601, used to select the codebook used for reporting the precoding matrix indicator PMI from the two-level codebook, and select PMI from the codebook; the two-level codebook includes a codebook reflecting long-term/broadband information And a codebook reflecting short-term/frequency selective channel information;

0052The CQI calculation unit 602 is used to determine the parameters used when calculating the channel quality indicator CQI, and calculate the CQI according to the parameters; wherein, when reporting through the PUCCH, the determined parameters used for calculating the CQI include the user terminal through the PUSCH Reported PMI; when reporting via PUSCH, the determined parameters used in calculating CQI include the PMI reported by the user terminal via PUCCH;

0053The reporting unit 603 is configured to report the PMI selected by the RI and the PMI selection unit 601 and the CQI calculated by the CQI calculation unit 602 according to the specified reporting mode.

0054For the process of reporting channel state information through PUCCH, the PMI selection unit 601 in the user terminal device selects a codebook reflecting long-term/broadband information, and selects from the selected codebook the precoding matrix corresponding to the full bandwidth. PMI; for the process of reporting channel state information through PUCCH, the unit selects a codebook reflecting short-term/frequency selective channel information, and selects from the codebook the PMI corresponding to the precoding matrix selected for each frequency domain reporting unit.

0055When reporting through the PUCCH, the PMI selection unit 601 can determine whether the RI exceeds a set threshold R_T; If the RI does not exceed R_T, Then select a codebook that reflects long-term/broadband information, and select a PMI corresponding to the precoding matrix suitable for the full bandwidth from the codebook. The unit can also judge that the RI exceeds R_TAt this time, a codebook reflecting short-term/frequency selective channel information is selected, and a PMI corresponding to a precoding matrix suitable for the full bandwidth is selected from the codebook.

0056When reporting via PUCCH, the CQI calculation unit 602 in the user terminal device may determine whether the RI exceeds a set threshold R_T; If the RI does not exceed R_TThen, the parameters used when calculating the CQI include: the RI, the PMI selected by the user terminal, and the PMI reported by the user terminal through the PUSCH. In judging that the RI exceeds R_TAt this time, the parameters used by the unit to calculate the CQI include: the RI, the PMI selected by the user terminal, and a fixed parameter; the fixed parameter is ^ ><^, where, Ν_τThe number of transmit antennas for the base station.

0057When reporting through the PUSCH, the CQI calculation unit 602 in the user terminal device may determine whether the RI exceeds a set threshold R_T; If the RI does not exceed R_T, The parameters used when calculating the CQI include: the RI, the PMI selected by the user terminal, and the PMI reported by the user terminal through the PUCCH. In judging that the RI exceeds R_TAt this time, the parameters used by the unit to calculate the CQI include: the RI, the PMI selected by the user terminal, and a fixed parameter; the fixed parameter is ^ ><^, where, Ν_τThe number of transmit antennas for the base station.

0058Through the description of the above embodiments, those skilled in the art can clearly understand that the present invention can be implemented by means of software plus a necessary general hardware platform, and of course, it can also be implemented by hardware, but in many cases the former is a better implementation the way. Based on this understanding, in the technical solution of the present invention, the computer software product is stored in a storage medium, and includes several instructions to enable a computer device (which may be a personal computer, server, or network device, etc.) to execute various embodiments of the present invention The method.

0059Those skilled in the art may understand that the drawings are only schematic diagrams of a preferred embodiment, and the modules or processes in the drawings are not necessarily required to implement the present invention.

0060Those skilled in the art may understand that the modules in the device in the embodiment may be distributed in the device in the embodiment according to the description of the embodiment, or may be changed correspondingly in one or more devices different from the embodiment. The modules in the above embodiments may be combined into one module, or may be further split into multiple sub-modules.

0061The sequence numbers of the above embodiments of the present invention are for description only, and do not represent the advantages and disadvantages of the embodiments.

0062The above discloses only a few specific embodiments of the present invention, but the present invention is not limited to this, and any changes that can be thought by those skilled in the art should fall within the protection scope of the present invention.